It takes a deft touch to draw a decent heart in latte foam, but that's not the hardest part about working as a barista. The real backbreaker: cheerfully greeting a hundred people in a row, even that one guy who hasn't left a tip in three years but always complains that his coffee isn't hot enough except for the times that it's too hot.

For baristas, salespeople, flight attendants, and many other service workers, fake smiles and forced pleasantries often come with the job description. But psychologists warn that emotions can't just be flipped on like an espresso machine, and smiles aren't as easy to put on as name tags. Feigning feelings at work — what psychologists call "emotional labor" — can be as mentally and physically taxing as any other type of workplace stress, but few workers or employers recognize the threat, says Neal Ashkanasy, a professor of business management at Queensland University in Brisbane, Australia. "People just put expressions on their faces without any idea what kind of stress it's causing," he says.

Alicia Grandey, a psychologist at Pennsylvania State University and a leader in emotional labor research, had to put on a happy face as a barista at Starbucks before she started grad school in the 1990s. "I'm a reasonably social person, but it was exhausting," she says. "I would come home from a day of barista-ing and my face would hurt. I thought I was just being whiny." Now she knows what was really happening: The sheer effort of expressing emotions she wasn't always feeling was wearing her down, one smile at a time.

Emotional labor taxes some of the deepest parts of the psyche. As Ashkanasy explains, genuine smiles, laughs, frowns, and other outward signs of true emotions mostly flow from the amygdala, a part of the brain that shapes our most fundamental impulses, from fear to lust. Putting on a fake emotion means going against the wishes of the amygdala, a piece of anatomy that's used to getting its way. "Your brain has to do a lot of work to keep that under control, and it uses physical resources to do it," Ashkanasy says.

That kind of effort is more than just tiring. Over time, it could become unhealthy.

"If your feelings are different from what you're showing, you can start to get back strain, neck strain, and stomachaches," Grandey says. The toll of emotional labor at work can follow people after hours, too. A 2013 study of bus drivers found that those who reported faking emotions during the day were more likely to suffer from insomnia, anxiety, and emotional exhaustion at home. A 2014 study of hotel managers by Grandey and colleagues found that people who had to feign their feelings on the job tended to be less helpful at home, presumably because they were too tired to pick up a broom or dishrag. And in yet-to-be-published research, Grandey and colleagues also found that people who fake positive emotions at less-than-positive jobs tend to drink more alcohol at home, perhaps because they feel inclined to cut loose after keeping things buttoned up. Other studies have suggested a similar lack of control with food. "You feel like you don't have any willpower," Grandey says.

Like any other task, emotional labor is easier for some people than others, Ashkanasy says. People who are naturally cheerful will have less trouble embracing the joy of scanning groceries or refilling baskets with bread sticks. They won't have to expend as much effort putting on a brave face, which makes it easier to thrive at their work, at least for a while.

Those who aren't actually happy with their work have another option: actively creating emotions needed for a job. Like a method actor trying to get into a role, a flight attendant could convince himself that he enjoys performing safety demonstrations that nobody watches. "You can try to recall moments that connect to the emotional state that you want to be in," Ashkanasy says. You aren't standing there holding an oxygen mask for the 1,488th time, no. "You're hanging out at a great party."

Once it's perfected, the acting approach can lessen much of the sting of emotional labor. After all, it doesn't take much effort to smile if you're actually happy. But if your name isn't Daniel Day-Lewis, method acting takes effort and training, something that few employers are able or willing to provide. "When I worked at Starbucks, we had two-week training that included role-playing situations with customers," Grandey says. "They don't do that anymore." (Starbucks did not respond to a request for comment before publication.)

It's not just corporate culture that makes life difficult for service employees; the national culture matters, too. While Americans expect bottomless reserves of cheerfulness from service workers, customers in some other countries can be more forgiving. A 2005 study by Grandey and colleagues found that employees in France don't suffer as many consequences from emotional labor, partly because being rude and gruff on the job is a bit of a French tradition. "If they're smiling, it's because they want to," Grandey says. "They don't have the same requirements about 'service with a smile' as the U.S."

Expectations in U.S. restaurants and coffee shops aren't likely to change soon, but employers can still take steps to lessen the strain of emotional labor. Ideally, Grandey says, all service employees would have a break room outside of the public eye where they could truly be themselves, at least for a little while. Also, she says, bosses and supervisors who expect smiles from their employees should try to promote a supportive work atmosphere — fake smiles take less effort when you're not getting yelled at behind the scenes.

Employers can also help their workers by encouraging them to think about the pleasant customers they meet throughout the day, not the few bad actors, says Allison Gabriel, a business psychologist at the University of Arizona. And if the public learned more about emotional labor, perhaps they would show a little more sympathy, making jerkish encounters fewer and farther between. "When I see a service employee who is not smiling or who is not super enthusiastic, I'll stop and say, 'How is your day going?'" Gabriel says. "I remind myself that their job may look simple, but so much of their job is managing their emotions to make my experience better. We don't give them enough credit."

This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.